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Grafted Chains (grafted + chain)
Selected AbstractsSurface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006Yan-Xin Liu Abstract Multiwall carbon nanotube (MWNT) was grafted with polyacrylate- g -poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid-treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X-ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880,6887, 2006 [source] Preparation of novel poly(ethylene oxide- co -glycidol)-graft-poly(,-caprolactone) copolymers and inclusion complexation of the grafted chains with ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2006Juan Huang Abstract A well-defined comblike copolymer of poly(ethylene oxide- co -glycidol) [(poly(EO- co -Gly)] as the main chain and poly(,-caprolactone) (PCL) as the side chain was successfully prepared by the combination of anionic polymerization and ring-opening polymerization. The glycidol was protected by ethyl vinyl ether to form 2,3-epoxypropyl-1-ethoxyethyl ether (EPEE) first, and then ethylene oxide was copolymerized with EPEE by an anionic mechanism. The EPEE segments of the copolymer were deprotected by formic acid, and the glycidol segments of the copolymers were recovered after saponification. Poly(EO- co -Gly) with multihydroxyls was used further to initiate the ring-opening polymerization of ,-caprolactone in the presence of stannous octoate. When the grafted copolymer was mixed with ,-cyclodextrin, crystalline inclusion complexes (ICs) were formed, and the intermediate and final products, poly(ethylene oxide- co -glycidol)- graft -poly(,-caprolactone) and ICs, were characterized with gel permeation chromatography, NMR, differential scanning calorimetry, X-ray diffraction, and thermogravimetric analysis in detail. The obtained ICs had a channel-type crystalline structure, and the ratio of ,-caprolactone units to ,-cyclodextrin for the ICs was higher than 1:1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3684,3691, 2006 [source] Reversible addition,fragmentation chain-transfer graft polymerization of styrene: Solid phases for organic and peptide synthesisJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002Leonie Barner Abstract The ,-initiated reversible addition,fragmentation chain-transfer (RAFT)-agent-mediated free-radical graft polymerization of styrene onto a polypropylene solid phase has been performed with cumyl phenyldithioacetate (CPDA). The initial CPDA concentrations range between 1 × 10,2 and 2 × 10,3 mol L,1 with dose rates of 0.18, 0.08, 0.07, 0.05, and 0.03 kGy h,1. The RAFT graft polymerization is compared with the conventional free-radical graft polymerization of styrene onto polypropylene. Both processes show two distinct regimes of grafting: (1) the grafting layer regime, in which the surface is not yet totally covered with polymer chains, and (2) a regime in which a second polymer layer is formed. Here, we hypothesize that the surface is totally covered with polymer chains and that new polymer chains are started by polystyrene radicals from already grafted chains. The grafting ratio of the RAFT-agent-mediated process is controlled via the initial CPDA concentration. The molecular weight of the polystyrene from the solution (PSfree) shows a linear behavior with conversion and has a low polydispersity index. Furthermore, the loading of the grafted solid phase shows a linear relationship with the molecular weight of PSfree for both regimes. Regime 2 has a higher loading capacity per molecular weight than regime 1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4180,4192, 2002 [source] Hybrid Aluminum Colored Pigments Based on Gradient Copolymers DesignMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2009Mathieu Joubert Abstract A colored polymer/aluminium hybrid pigment was synthesized by nitroxide mediated polymerization initiated from an inorganic surface. This approach requires the preparation of a vinyl dye monomer able to copolymerize with n -butyl acrylate (n-BuA) and styrene (S) from the surface of aluminium flakes. The linearity of the ln([M]0/[M]t) and of the as a function of time and conversion constitute the criteria of control/"living" polymerization, i.e. linearity of respectively ln([M]0/[M]t),=,f(t) and the ,=,f(conversion) plots. Kinetic measurements reveal an upward deviation from the linearity for n -BuA polymerization for very high conversion. The introduction of S monomer restores the control of the polymerization. Both the length of the grafted chains and the dye/styrene molar ratio influence the color of the hybrid material. [source] Formation of Inorganic/Organic Nanocomposites by Nitroxide-Mediated Polymerization in Bulk Using a Bimolecular SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2004Julien Parvole Abstract Summary: A series of organic-inorganic nanoparticles were synthesized by nitroxide-mediated polymerization (NMP) of butyl acrylate initiated by a self-assembled monolayer of an azo initiator. The azo initiator was immobilized on silica particles in the presence of a stable nitroxide radical, SG1 (an acyclic , -phosphonylated nitroxide, N - tert -butyl- N -(1-diethylphosphono-2,2-dimethyl)propyl nitroxide). After preliminary qualitative characterization by X-ray spectroscopy (XPS) and Fourier-transform infrared (FTIR) measurements, the nanoparticles were studied by thermogravimetric analysis (TGA) to determine the polymer grafting density and to permit a comparison with corresponding values of the initiator monolayer. It was demonstrated that the grafting from polymerization exhibits a controlled character with a low polydispersity (,<,1.2) in a large range of molecular weights of the grafted chains (from 4,000 up to 145,000 g,·,mol,1) under the conditions when the stable radical SG1, acting as chain growth moderator tethered to the inorganic core, was used. [source] Ceric(IV) ion-induced graft copolymerization of acrylamide and ethyl acrylate onto cellulosePOLYMER INTERNATIONAL, Issue 2 2006Prof. Kailash C Gupta Abstract Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (FAAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10,2 to 60.0 × 10,2 mol L,1, whereas the composition of the grafted chains (FAAm) was found to be dependent on feed composition (fAAm) and reaction temperature. The effects of ceric(IV) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10,3 mol L,1 concentration of CAN at a feed molarity of 30.0 × 10,2 mol L,1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10,3 mol L,1) at a constant concentration of nitric acid (5.0 × 10,2 mol L,1). The composition of the grafted chains (FAAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r1) and ethyl acrylate (r2) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r1 = 0.54 and r2 = 1.10, respectively, and hence the sequence lengths of acrylamide (m,M1) and ethyl acrylate (m,M2) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r1 × r2) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ,squares' of the concentrations of the comonomers and on the ,square root' of the concentration of ceric ammonium nitrate. The energy of activation (,Ea) of graft copolymerzation was found to be 5.57 kJ mol,1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry [source] | ||||||||||